Electrical apparatus.



Patented Oct. 3, 1916.

J S. PRESTON. ELECTRlGAL APPARATUS.

APPLICATION FILED DEC.30, 1914.

Inventor: J innleg Preston, 3

Fig. 4

J/ W Fig.5.

W itn esses His fittorneg.

ransron, or scnn nacranmnaw roan, Assmn'on r0 GENERAL ELECTRIC COMPANY,A. CORPORATION OF NEW YORK.

anagrnrcar. urana'rns.

To aZZwkom it may concern:

Be it known that I, J STANLEY PRas'roN, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, havemvented certain new and useful Improvements in Electrical Apparatus, ofwhich the following is a specification.

My invention relates to a number of types of electrical apparatus likelyto be dama ed through resonating with abnormal requencies; it ishowever, particularly applicable to transformers, and for the sake ofsimplicity, I shall mostly describe but its aplication to suchapparatus. .The extent of its application to other apparatus, and howsuch applications may be made, will be r adily understood from thedescription 0 its ap lication to transformers.

s is well known, any electrical apparatus. or portion of electricalapparatus having both inductance and capacity, may oscillate or resonateat some certain frequency deendent upon the values of these features.Now for ap aratusto resonate as a whole is not particu arly dangerous,for protective devices as of the over-voltage type, are readily a pliedat the terminals of the apparatus to ta (e care of such conditions. Suchcases occur when the impedance factors of' the aparatus are uniformlydistributed between its terminals. When however, the electrostatic,capacity of the apparatus for example, is not uniformly distributedthroughout the apparatus, the continuity of the apparatus is broken.Then portions of the apparatus may resonate substantially independentlyof the other portions thereof and of the apparatus as a whole, and oneor more of those portions may develop a dangerously high volta e withoutany manifestation at the termina s of the apparatus (with the possibleexception of an abnormally high frequency manifestation of a value notan erous to the apparatus as a whole, and of ow voltage). Suchdiscontinuous capacity distributions occur very frequently intransformers, wherein commonly each winding is (or may Specification ofLetters Patent. .4pplicat1on filed Deiaember 30, 1914. Serial No.879,791.

Patented Oct. 3, 1916.

be described as) comprised of straight series connected colls assembledin groups, the groups being separated from each other for ventilation orto allow the insertion of portions of the other winding, or for otherpurposes. The capacity of the two coils forming the adjacent faces oftwo such adjacent groups of-the same winding, is considerably less thanthe capacity of two similar coils both of which are located within asingle group, and hence the electrostatic displace 'ment between any twoadjacent coils within a single group is greater than that between twoadjacent face coils of-difl'erent groups.

These differences of capacity and displace-.

ments are due both to the difference in spacing between coils and to thedifference be tween the s ecific inductive capacities of the dielectricsbetween the coils; between the coils of any single group, some soliddielectric is commonly used, while between groups (and hence betweenadjacent face coils of different groups) the principal dielectric iscommo y oil or air, the specific inductive capacities of both of whichare considerably lower than those of the common solid insulations. Inshort in transformers as commonly constructed, the energy of any windingis not uniformly distributed along its length.

The object of my invention then, is to overcome the ill effects of sucharrangements of coils (or' broadly, such non-uniform distribution ofcapacity) and to maintain the electrical continuity of the ap aratusbetween its terminals and the uniibrm distribution of the energythereof. To do this I may be said to provide for substantially equaldisplacements between all the faces of the internal coils (or whateverthe conductors of the apparatus may be), presupposing that the coils areof the same size, or I relate the capacities of, pairs of adjacent coilsto inductances of values inversely proportional to the values of'therespective capacities. However, since separating the groups also bringsabout differences in the mutual inductlons of adjacent coils and otherincidental effects, and since the coils may sometimes be of differentsizes, 1t may sometimes be undesirable, or even unnecessary for these orother reasons, to exactly 01 ualize the displacements or the products ofthe capacities by their respective inductances' to bring aboutthedesire-d degree of continuity; however herein, including the claims, Ishall refer to only such equalities, or substantial equalities, andsimilar conditions, and must be understood as including thereby allthese special cases so far as may be or as indicated. 'lhese specialcases are too numerous to mention, are. fairly uncommon, and areunmxcessary for an understanding of my invention and as they arise willbe readily un-- derstood by those skilled in the art.

To equalize the displacements, I propose to impress greater, voltagedifferences between those adjacent coils separated by the greaterdistances and by dielectrics of lower specific inductive capacity (asthe adjacent fare coils of different groups), than are impressed betweenother adjacent coils. Preferably, to produce exact equalities ofdisplacenamts, the voltage differences between all adjacent coils aremade directly proporfour groups, 1, 2, 3 and 4. The other wind ing isillustrated as of the simple cylindrical type and does not here embodymy invention though my invention is not limited in its application toany single tvpe of-windin or to one of a plurality of windin s. becapacities of the different pairs 0 coils of any group, as for exampleof the group 1, are equal, for the coils are all alike and adjacent-twos are separated by equal distances and by the same dielectricmaterial; they are connected in straight series and therefore thevoltage differences are equal; the displacement between any two adjacentcoils of a group is therefore equal to that between any other twoadjacent coils of that group. Also the displacement between any twoadjacent coils'of any single group is tional to the distances betweenthe coils and Y inversely proportional to the specific ind-netivecapacities of the dielectrics between them (the areas of the coils beingequal and the mutual 'inductances sufficiently equal). Practically, formost common constructions this may be brought down to employing theusual group construction wherein the capacities and voltage differencesper pair of coils are substantially equal, and to simply arranging for agreater voltage difference between the two coils adjacent each spacebetween groups. This, may be simply, and preferably is, done, by thesystem of coil connections which is described hereinafter in detail,this system of connections in turn brings about the hereinbeforementioned capacity-inductance relation. The specific apparatus in whichmy invention may be embodied is however, subject to considerablemodification.

In the following detailed description and the accompanying drawin I havedescribed and diagrammatically il ustrated various embodiments of myinvention.

Figure 1 is an elevation, partly in section, of a transformer embodyingmy invention in one of its windings. Figs. 2 and 3 are diagrammaticrepresentations of windings of use in explainmg my invention. Figs. 4and v5 illustrate windings with some other connections embodying myinvention.

In the transformer of Fi 1, all the coils of the outer winding are a ikeand are assembled in groups of four separated for ventilation; in thistransformer there are equal to that between any other two adjacent coilsof that or any other single group, since the coils and groups and. v0tages are alike. According to the prior practice, all the coils of thiswinding would be connected in straight series. The discontinui ties ofthe winding would occur then between each two groups of coils, forbetween the adjacent face coils, for example coils 10 and 11, of thedifferent groups 1 and 2, the capacities are considerably less thanbetween adjacent coils of any sin 1e group, for example coils 11 and 12'of group 2, while equal voltage differences would exist between each twoadjacent coils, irrespective of their location; this results of course,in smaller displacements between adjacent face coils of different groupsthan between adjacent coils of any single group. According to myinvention however, while I connect the coils of each sin le groustraight series and connect al the 0011s in straight'series in effect,that is so that none buck the others, the face coil of each grou is notconnected to the adjacent face 0011 of the adjacent group, but, in thisarticular case, it is connected to the far ace coil of that adjacentcoil, so that there exists a voltage difference of a full group of coilsacross each space. Thus the face coil 10 of group 1 is connected to coil14 of group 2, and coil 15 of group 3 is connected to coil 11 of grou 2,and so on through the winding. In a dition, the whole is so designedthat the voltage of a group is sufficient to produce substantially thesame displacement in the smaller capacity between each two adjacent facecoils, as 10 and 11, as takes place under the smaller voltage in thegreater capacity between each two adjacent coils as 11 and 12, ofasingle group. In accomplishing this it is necessary of course, that thevoltage difference between physically adjacent coils be inverselyproportional to their capacities, or directly proportional to 7 theirdistances apart and inversely proporthe coils bein equal).

. and the coils 11 an 12'.

tional to the specific inductive capacity of the ldielectrlcs etween them (the areas of By some, t e invention will be better understoodperhaps by a consideration of Fi s. 2 and 3. These figuresdiagrammaticafiy illustrate the principal inductance and capacityrelations of two windings each comprising two groups of coils similar inconstruction and location to the groups 1 and 2 of Fig. 1; they may betaken as equivalent circuits in which the inductive and capacityrelations concerned by my invention are separated. The coil parts ofthese figures bear reference characters similar to those borne by thephysically similar parts of Fig. 1. Fig. 2 illustrates all the coilsconnected in straight series as has been the common practice heretofore;Fi 3 illustrates the coils connected in accor ance with my invention asexplained with reference to Fig. l and as may be understood from aninspection of Fig. 'In both cases as well as in the case illustrated inFig. 1, a current traversing the winding from one terminal to the other,circulates in the same direction about the core in all the coils. Thecondensers including 21, 22 and 23, indicate the capacity relationsbetween the coils; the plates of the condensers are of the sames1ze'since the coils are presumed to be of the same size; the plates ofcondenser 22 are separated about four times the distance between theplates of' condensers 21 and 23 and the others, since the capacity ofthe coils 10 and 11 (and likewise of 10' and 11'), the adjacent facecoils of adjacent groups, is assumed in this case to work out to be butone-fourth of the, capacity of two adjacent coils of a single rou as thecoils 11 and 12 Now, as is well known, the periodic time of oscillationof any portion of electrical apparatus may be represented by T=7c /LG:

Assume the capacity of each condenser except condenser 22, to be C;the'capacity of 22 is then 0/4 by prior assumptlons.

' Each condenser spans approximately two half coils or one completecoil; assume the inductance of each two half coilsto be L. In Fig. 2,the local circuit formed by condenser 23 and one-half of coil 11' andonehalf of coil 12', has then for its periodic time of oscillation,

T le- 1L0; with the exception of the local circuit includin condenser22, every other .loc al c1rcuit 0 Fig. 2 has the same periodic time ofoscillation since each is exactly similar to the circuit of condenser23. The periodic I '65 I time bf the local circuit includin condenser22, half of coil 10 and half o coil 11f is I however, I

aui/ 5m or the natural frequency. local circuit is double that of "each"of the others.

This winding is'thus, discontinuous between the groups. In Fig. 3, everylocal circuitexcept that mcludmg condenser 22 has likewise periodic timerepresented by was; the local circuit including condenser 22 has aperiodic time represen ted by siiice it spans or includes in itscomplete local circuit, four complete coils (one half of coil 10, all ofcoils 14, 13 and\12, and the right hand half of coil 11) rather than onecomplete coil; this reduces to or the natural frequencies of all thelocal circuits of this winding are equal. The Whole of the winding ofFig. 3 is therefore electrically continuous from one terminal to theother.

The winding of Fig. 4 contains certain modifications and extensions ofthe invenlacements between the groups are equal (it ein-g presupposedthat the dielectrlcs are alike) and designed 'tobe-equal to thosebetween adjacent coils of any single group. Between groups 30 and 31 andbetween groups 31 and 32 the distances are each (5), and the voltagedifference across each group is equal to that of five-coils or one ofthegroups as indicated. Between the groups 32 and 33 the distance is (3)and the voltage across it is that of. the small group 33 of three coils.Between groups 33 and 34 the distance is (8), and the voltage differencebetween the adjacent face coils of thesetwo groups is that ofboth groups33 and 34 or eight coils. i

Fig. 5, drawn on the same plan as Fig. 2, illustrates a windingembodying my invention in which certain of the connections extendbetween other than the physically adjacent groups. p This arrangement isparsufficient to equalize the displacements between every two adjacentcoils.

While I have described the principle of my invention and the best mode Ihave contem lated for applying this rinciple, other m ifications willoccur to t ose skilled in,

this iart' and I aim in the ap ended claims to ,cover all modificationswh1ch do not involve a departure from the spirit and scope of myinvention.

What I claim as'new and desire tosecure by Letters Patent of the UnitedStates, is:

- 1. An electrical winding comprising a plurality of coils arranged inseparated groups, connections extending between each two adjacentgroups,the connection between each two adjacent groups extending fromthe far coil of one of those groups to a coil of the other group.

2. An electrical winding comprising a plurality of coils arranged inseparated groups, connections extending between each two adjacentgroups, the connection between each two connected groups extendingbetween two coils of those those coils forming the ad acent faces of thegroups. 5 j

3. An electrical winding comprising a plurality of coils having di erentcapacities per pair of adjacent coils and so connected that thedisplacements between adjacent coils are substantially equal.

4. An electrical winding comprising a plurality of coils havingdifferent capacities per pair of adjacent coils and so connected thatthe voltages established between adjacent coils are inverselyproportional to the capacity thereof.

5.. Electrical apparatus comprising a plurality of conductors havingdifferent capacities per pair of adjacent conductors wherein the voltagebetween each two adjacent conductors is inversely pro ortional to thespecific inductive capacit o the insulation therebetween and is directlyproportional to their distance apart.

6. An electrical winding comprising a plurality of coils arranged inseparated groups, connections extending between each two adjacentgroups, the connection between each two adjacent groups extendingbetween two coils of those groups other than those coils forming the adacent faces of the groups, and including within its span a sufficientnumber of coils to establish a voltage between the two adjacent facecoils of the groups substantially inversely proportional j acent coioups other than.

to their capacity relative to the capacit and voltage difference betweeneach two a s of a single group.

, 7. An electrical winding comprising a plurality of coils arranged inseparated groups, connections extending between each two adjacentgroups, the connection between each two adjacent groups extending fromthe farcoil of one of those groups to a coil of the othergroup "andincluding within its span a sufficient number of coils to establish avoltage between the two adjacent face coils of the groups substantiallyinversely proportional to their capacity relative" to'the capacity andvoltage difference between each two adjacent 0011s of a single group.

8. An electrical winding comprising a plurality of coils arranged inseparated groups, connections extending between the groups, therespective connections e'xtendmg between such coils of the groups as toestablish a voltage between each two adjacent face coils of differentgroups which is substantially inversely proportional to the capacity ofthe respectlve coils relative to the Voltage difference and ca acitybetween each two adjacent coils of a single group.

9. An electrical winding comprising a I 10. An electrical windingcomprising a plurality of coils arranged in separated groups,connections extendin between the groups, the respective connectionsextending between such coils of the groups as to relate the ca acity ofeach two adjacent face coils of di erent groups to an inverselyproportional inductance relative to the capacity and its relatedinductance of each two adjacent coils of a single group.

11. An electrical wind1ng comprising a plurality of coils arranged inseparated groups, connections extending between the adjacent groups, therespective connections extending between such coils of adjacent groupsas to relate the capacity of each two adjacent face coils of adjacentgroups to an inversely proportional inductance relative to the capacityand its related inductance of each two adjacent coils of a single group.

12. An electrical windin comprising a plurality of coils having di erentcapacities per pair of adjacent coils and so connected that each suchcapacity is related to an inversely roportional inductance.

13: E ectrical apparatus comprising a plurality of conductors havingdifferent capacities per pair of adjacent conductors,

wherein each such capacity is related to an In witness whereof I havehereunto set inversely proportional inductance. my hand this 29th day ofDecember, 1914:. 10

14. Anelectrical winding comprising a plurality of coils havingdifferent capacities J STANLEY PRESTON.

per pair of adjacent coils and means for connecting the coils and forproducing sub- Witnesses:

stantially equal displacements between ad- HELEN Onrom),

jacent coils. MARGARET E. WOOLLEY.

